1.4.7 Region Commands

Vi operators like d, c etc. are usually used in combination
with motion commands. It is now possible to use current region as the
argument to these operators. (A region is a part of buffer
delimited by point and mark.) The key r is used for this purpose.
Thus d r will delete the current region. If R is used instead
of r the region will first be enlarged so that it will become the
smallest region containing the original region and consisting of whole
lines. Thus m . d R will have the same effect as d d.